Fullers Earth, an unctuous sort of clay, much of it kaolinite, useful in fulling cloth, from its property, common to aluminous earths, of absorbing oil and grease. That variety of clay is preferred which falls to pieces when put in water, making a slight crackling sound. Its colors are various shades of yellowish, greenish, bluish, brown, and gray; lustre dull, but appears greasy when rubbed. Its composition is given by Dr. Ure as follows: silica 53, alumina 10, peroxide of iron 9.75, magnesia 1.25, lime 0.5, water 24, potash a trace. Dr. Thomson found silica 44, alumina 23.00, protoxide of iron 2, magnesia 2, lime 4.08, water 24.95. It is not now esteemed of so much value as formerly, soap having taken its place. In England it used to be so highly valued that its exportation was prohibited. When used, it was first dried by the sun or by fire, and then thrown into cold water. The powder thus formed was sorted by washing into coarse and fine qualities, the former of which were applied to inferior, the latter to finer cloths.